gpt-oss-120b vs LLM-jp-3.1 8x13B instruct4
Pricing, context window and real answers (August 2026)
gpt-oss-120b (OpenAI) and LLM-jp-3.1 8x13B instruct4 (Llm Jp), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
| LLM-jp-3.1 8x13B instruct4 | ||
|---|---|---|
| Provider | OpenAI | Llm Jp |
| Input (per 1M tokens) | ¥16 | ¥16 |
| Output (per 1M tokens) | ¥79 | ¥79 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥56 | ¥56 |
| Context window | 131,072 tokens | 4,096 tokens |
| Release date | 8/5/2025 | 3/21/2026 |
| Input modalities | text | text |
| Arena · overall | #196 · ELO 1,352 | Unranked |
| Arena · Japanese | #133 · ELO 1,328 | Unranked |
| Arena · coding | #203 · ELO 1,391 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- Output pricing is identical (¥79 per 1M tokens).
- For long documents, gpt-oss-120b: a 131,072-token context window against 4,096 for LLM-jp-3.1 8x13B instruct4.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
gpt-oss-120b
LLM-jp-3.1 8x13B instruct4
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
gpt-oss-120b
LLM-jp-3.1 8x13B instruct4
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
gpt-oss-120b
LLM-jp-3.1 8x13B instruct4
Frequently asked questions
- Which is cheaper, gpt-oss-120b or LLM-jp-3.1 8x13B instruct4?
- Both are ¥79 per 1M output tokens on FastMetal (yen, before tax).
- How do the context windows of gpt-oss-120b and LLM-jp-3.1 8x13B instruct4 compare?
- gpt-oss-120b takes 131,072 tokens; LLM-jp-3.1 8x13B instruct4 takes 4,096.
- Can I use gpt-oss-120b and LLM-jp-3.1 8x13B instruct4 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-oss-120b" or "llm-jp-3.1-8x13b-instruct4" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call gpt-oss-120b and LLM-jp-3.1 8x13B instruct4 from the browser chat and the API. No monthly fee.